1. Technical Field
The disclosure relates to a method for signal processing in a receiver that can be tuned to different carriers, wherein the analog signal received via an antenna is filtered and amplified in a first method step and is converted into a baseband frequency and filtered in a second method step, and, in a third method step, a digital signal is generated from the analog signal by means of an analog-to-digital conversion, and, in a fourth method step, the digital signal is filtered and subsequently decoded and the decoded data are output.
The disclosure also relates to an arrangement for implementing the method that includes a receiver having an antenna input, to which an antenna is connected and which has on the output side a bandpass filter and a baseband arrangement connected downstream of the receiver and having an input-side analog-to-digital converter, which is connected to the bandpass filter, and an output for outputting the decoded data.
2. Description of the Related Art
For the transmission of a signal of interest it is customary, not just for wireless transmission methods, to convert the signal of interest to be transmitted, which includes the information items to be transmitted, into a so-called carrier signal—or the carrier for short. The carrier represents a temporally variable quantity, for example a current or a voltage, which changes in at least one of its parameters such as frequency, phase, amplitude, duty ratio depending on the signal of interest. Thus, upon application of a QPSK modulation, for example, the signal of interest is mapped in the phase angle of the carrier, wherein two cosinusoidal signals of the same frequency with a phase shift of 90° with respect to one another are utilized as carrier in this case in order to transmit both a real part and an imaginary part. After this step—also referred to as modulation of the carrier—and transmission via a transmission channel, the signal of interest is recovered in a receiver by means of a demodulation method. For this purpose, it is necessary to tune the receiver to a specific carrier having the signal of interest in its modulated form.
DVB-H is a promising standard for the transmission of offered digital television contents for mobile TV receivers. DVB-H is based on the existing DVB-T standard and uses existing DVB-T transmission devices and the existing infrastructure. Transmission is provided in the existing TV frequency channel of the UHF band. Consequently, the bandwidth corresponds to the bandwidth of the analog TV frequency channels, which is dependent on the prevailing standard in the respective country and has a value of 6, 7, or 8 MHZ.
A DVB-H variant in which the L bands are used is additionally specified. A bandwidth of 5 MHz in accordance with the L band channel spacings is defined for this variant. DVB-H networks of this type are constructed in many countries in Europe. Other countries, for example the USA and China, are considering the use of DVB-H networks for a limited period.
Another standard for providing TV content for mobile devices is T-DMB. As in DVB-H, the use of existing transmission devices is possible in T-DBM, too. In this case, however, use is made of existing transmission devices according to the DAB standard (digital audio broadcasting), which uses a bandwidth of 1.6 MHz and a third of the 8 MHz channel spacing. DAB is designed to work both in the VHF band and in the lower L band and for satellite reception below 3 GHz. T-DMB is used in Korea, for example. Other countries, such as Germany and Great Britain, promote both standards.
While China is currently developing its own standard DMB-H, this country is probably the first to allow provision of DVB-H and T-DMB networks and offered services until corresponding DMB-H devices are available.
In the case of large network operators which use broadcasting transmitters which enable both DVB-T- and DAB-based transmissions, there is the need to provide corresponding receivers which can receive both standards.
Mobile TV receivers, receivers for mobile telephones and small handheld devices differ significantly from those receivers which were originally developed for digital receiver applications (set-top box) or in the case of the DAB standard from car radios and other portable broadcasting receivers.
In the development of new receivers, which process more than one of the abovementioned standards, they are additionally intended to have a low energy consumption and small dimensions. Such properties are achieved only inadequately with known DVBT and DAB solutions.
Most semiconductor manufacturers offer, for mobile TV receivers, energy-saving silicon receivers which support the DVB-H standard, for example with the channel bandwidths of 5, 6, 7 and 8 MHZ. New developments will additionally have to support the T-DMB standard as dual-mode tuners.
In this case, although most of the known receivers meet the requirements with regard to the frequencies to be supported, which are necessary for applications of this type, they do not satisfy the required analog filter bandwidths for achieving the required frequency selectivity.
Consequently, new receiver layout developments are necessary. What is disadvantageous in this case is the fact that analog filters having a decreasing bandwidth have a larger space requirement and this is at odds with the trend towards further miniaturization.